Cupola furnace with heat regeneration means



Oct. 1, 1968 R. FORMENTI 3,403,897

CUPOLA FURNACE WITH HEAT REGENERATION MEANS Filed Oct. 23, 1966 5 Sheets-Sheet l V 5 n-t l-- x 7 1 1: I E: 55 ii :5 E L/ :i i 1 1/ /:E il

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CUPOLA FURNACE WITH HEAT REGENERATION MEANS Filed Oct. 25, 1965 s Sheets-Sheet 2 F/g. 1b e- 26 H7 III 25 -27 28' 3 29 g; I j I 33 i if; 40?

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v CUPOLA FURNACE WITH HEAT REGENERATION MEANS Filed Oct. 23, 1965 5 Sheets-Sheet 5 United States Patent 3,403,897 CUPOLA FURNACE WITH HEAT REGENERATION MEANS Riccardo Formenti, Via Monte Grappa 27, Galliate, Novara, Italy Filed Oct. 23, 1965, Ser. No. 503,144 8 Claims. (Cl. 266-30) ABSTRACT OF THE DISCLOSURE A cupola furnace having a shell and a chimney surmounted thereon in which exhaust gases from the chimney and ambient air are fed in relative controlled amounts to the furnace inlet nozzles after passing in heat exchange relation around the furnace in the region of the smelting zone, the exhaust gases undergoing heat exchange with the interior of the furnace before being fed to the nozzles.

This invention concerns a cupola whose running cost is very low, particularly for the smelting of cast iron.

One of the objects of this invention is to provide a cupola where it is possible to convey heated hot air to the nozzles, thus regenerating the heat which would otherwise be scattered, by exploiting-right on the eupola-the heat of the gas released over the preheating zone of the cupola.

Another object is to convey heated air to the nozzles of the cupola, by making the air itself graze the wall of the cupola from the chimney to the smelting zone.

Another object is to heat the air to be conveyed to the nozzles without necessarily having to use additional fuel for this purpose.

Another object is to provide the possibility of conviewing to the nozzles, gas rich in CO and CO which is drawn over the charging zone and mixed with fresh air in adjustable quantities.

Another object is to provide a cupola whose metallurgical operation is adjustable and particularly where it is possible to obtain cast iron with a carbonium content whose percentage can be selected in a wide range of values, from a minimum to a maximum value.

Another aim is to provide a cupola with which it is possible to obtain cast iron whose maximum carbonium content is higher than that obtainable with normal cupolas.

Another aim is to provide a cupola whose nozzles can be stoked both with cold air and with warm air.

Another object is to provide a cupola including a device by which it is possible to dehumidify the air to a constant humidity.

The cupola according to the invention is formed by a sprue basin, a smelting zone, a preheating zone, a charging zone, a chimney, nozzles placed below the smelting zone, and means to convey the air under pressure to the nozzles. Adjustable devices to draw fresh air near the chimney top are also included, in addition to adjustable devices to draw the gas from inside the chimney, a wall which, together with the external surface of the chimney, forms a first hollow space to which are linked the above mentioned adjustable devices to draw fresh air and to draw gas, means to convey the air under pressure to the nozzles, including an intake flue connected to the above mentioned first hollow space and a throw flue connected to the nozzles.

There will next be described by way of example and not restriction an embodiment of a cupola according to the invention which is illustrated in the attached drawing, wherein:

FIGURES 1a and lb show, in longitudinal section, the upper and lower part respectively of a cupola and,

FIGURES 2, 3 and 4 are cross sections respectively 3,403,897 Patented Oct. 1, 1968 taken on lines II-II; IIIIII; and IV--IV in FIGURES 1a and 1b.

The cupola shown in the drawing includes a wall supported on a base 2 placed on columns 3.

Above the cupolas wall in correspondence therewith is a shell 1 made of metallic sheets, forming the so-called cupola chimney at the upper end of which are openings 5 for the outlet of the combustion gases of the coke stoked in the cupola together with the cast iron to be smelted, through the door 4.

The shell 1 forming the chimney is externally bounded by a wall 6 which, together with the external surface of the shell, forms a first hollow space which is open at the upper end where it is surmounted by a cover 7 defining an air intake through which fresh air is sucked into the above mentioned first hollow space in which will become clearly understandable from the following description.

In the first hollow space is inserted a transverse bafile 8 having a hole 9 adjacent an opening in the shell 1 of the chimney. The latter opening provides communication between the inside of the chimney and the above mentioned first hollow space, and the size of the opening is adjustable by means of a valve 10 secured on a rod 11 to which too is secured a valve 12 sliding in a pipe 13.

The rod 11 and valves 10 and 12 can be moved by means of a lever 14 in such a way to change, at the same time both the free passage area of the opening in the shell 1 and the free passage area between the first hollow space above bafile 8 and the inner part of the pipe 13, while always leaving the hole 9 completely free.

The position of the valve 12 and of the valve 10 can be determined from the outside of the cupola due to the presence of an index 15 secured to the rod 11 and movable in front of a graduated scale 16. Several longitudinal fins 17 project from the cupola shell 1 into the above mentioned first hollow space, above the transverse baffle 8; such longitudinal fins help to scatter and to transmit the heat of the gases rising in the chimney.

Below the baflle 8, the wall 6 of the first hollow space widens in order to accommodate other fins 18 which also project from the cupolas shell 1, and particularly to contain a pipe 19 which is wound as a spiral around the chimney and through which runs cold water. The function of the cold water is to eifect cooling of the gas and air running down along the hollow space by conditioning them, that is by causing the condensation of the vapor contained in them, thus reducing the humidity content to a uniform low value.

Below the spiral pipe 19 the wall 6 is shaped in such a way to form a basin wherein is collected the water of condensation which is removed by means of a pipe 20; to avoid that the water, which condenses near the pipe 19, may drip inside the hollow space, a cover 21, is provided below which the hollow space contains other fins 22 which project from the shell 1 and the space ends at the base of the chimney, right below the charging door 4, where it is delimited by a diaphragm 23.

Below the charging door 4 the cupola is bounded by a wall formed by a series of rings 24 made of heat-resistant cast iron; they are overlapped and form a continuance of the shell 1.

At the inside these rings define a gap with a slightly conical shape whose larger base is at the bottom and they are externally enclosed by a wall 25 which in turn is in continuation of wall 6.

Between the rings 24 and the wall 25 there is a second hollow space which at its upper end, is connected to the already mentioned first hollow space, through three rectangular openings 26 at intervals in the wall 25 (see FIGURES lb and 3).

Except for th e ring placed right below the charging door 4, the rings 24 have at their ends a rim 27 which is turned as if it were a transversal flange and in which there are three semicircular openings 28 placed at 120 intervals the openings 28 of adjacent rings 24 being offset.

Ribs 29 project from the external surface of the rings 24 and they extend lengthwise and they join the wall such ribs 29 are interrupted by semicircular ribs which, together with the openings 28 cause a meandering course of the air and gas running down in the second hollow space in order to cover the whole external surface of the cast iron rings.

Wall 30 and wall 25 cooperate with the diaphragm 23 and with a diaphragm 31 placed at the level of the lower rim of the lowest of the rings 24, to define an air-tight enclosure having insulating functions. Two walls 32 extend above the diaphragm 23 to the region right below the charging door thus dividing the air tight enclosure from the first hollow space.

The diaphragm 31 in the lower part delimits also the second hollow space which is in communication with a ventilator 33 by means of the intake pipeline 34 of the ventilator itself. The cast iron rings 24 and the airtight enclosure extend in the cupola below the charging door in a part of the cupola usually shown as charging zone.

A gatevalve 35 is operated by a lever 36 to control the degree of opening in the intake pipeline 34.

To the intake pipeline, between the point where the gatevalve is placed and the ventilator, is connected a pipeline 37 directly in communication with the ambient atmosphere and which too can be controlled by means of the same above mentioned gatevalve 35, so that when the pipeline 37 is completely closed by the gatevalve, the pipeline 34 is completely open and vice versa.

As it is clearly shown in FIGURE 11), in the intermediate positions of the gatevalve 35 there is intake at the same time both from the pipeline 34 and from the pipeline 37.

The ventilator 33 has a delivery flue 38 leading to a third hollow space between the shell 39 and a wall 40 which encloses the shell. This hollow space is open at the top and at the bottom is bounded by a horizontal surface 41 placed below the delivery flue 38 and it includes a balancing diaphragm 42 formed by a drilled disk placed above the delivery flue 38. This disk defines a passage of restricted area through which the air and the gas conveyed by the ventilator to the pipeline 38 are distributed uniformly and above the balancing diaphragm. The shell 39, is integrally faced with a refractory material 43 covered in turn by fire-bricks 44, and it extends from the horizontal surface 41 to the diaphragm 31 in a part of the cupola practically corresponding to the usually known preheating zone. Several longitudinal fins 45, which are traversed by the air and the gas blown by the ventilator into the third hollow space, project externally from the shell 39, above the diaphragm 42. The air and gas, after having reached the top of the third hollow space, flow down outside it into another hollow space defined by the external surface of the wall 40 and by the inner surface of another wall 46 and thence through a balancing diaphragm 47, similar to diaphragm 42, and is conveyed to the nozzles 48 and from here is blown inside the cupola.

A last wall 49, which, together with a diaphragm 31 and a disk 50, bounds an air-tight enclosure for heat insulation of the cupola, outside the wall 46.

The part of the cupola where the nozzles are placed is usually kown as the smelting zone, while the zone right below and closed by the base 2 is known as the sprue basin: the smelting zone and the sprue basin are covered inside by a refactory material and by fire-bricks and outside they are covered by a wall 51 of metallic sheets.

During the cupolas operating while the coke and the cast iron are stoked inside the cupola itself through the charging door 4, the ventilator 33, operated by an electric motor, causes a suction in the intake pipeline 34.

When the gatevalve 35 is kept in such a position to open the passage in the pipeline 34, a suction is produced in the first and second hollow spaces, which causes an intake of fresh air through the air intake at the top of the chimney at the cover 7. The air flows down along the first hollow space to pass the fins 17 and the shell 1 of the chimney, and it mixes with the gas sucked from inside the chimney through the valve 10 when the mixture is open and then it fiows down through the hole 9 to contact the fins 18 and the spiral pipe 19 where-at most of the water vapor condenses thereby reducing the humidity to a constant value: it is to be noticed that the valve 12, even when it is arranged in maximum shifted'position inside the chimney, is made in such a way that it never closes completely the passage of the air sucked from the top of the chimney: the air or the mixture of air and gas continues its downward motion passing the fins 22 and the shell of the chimney and it then flows through the openings 26 while it penetrates into the second hollow space Where it flows downwards with tortuous motion because of the presence and arrangement of the flanged rims 27 with their semi-circular openings and the ribs 29, with their openings. The air, which causes a strong cooling of the cast iron rings 26, is then sucked by the ventilator 33 through the pipeline 34, and then blown into the delivery flue. Obviously if the pipeline 34 is kept closed by means of the gatevalve 35, and at the same time the passage in the pipeline 37 is kept open, the ventilator sucks only fresh open air through the pipeline 34; other intermediate arrangements are possible too, that is with the pipelines 34 and 37 only partly closed. The air or mixture of air and gas, blown by the ventilator is admitted in the third hollow space below the balancing diaphragm 42 from where it is spread uniformly and with uniform pressure above the diaphragm itself. The air then flows upwards in the third hollow space passing the fins 45 and the shell 39 of the cupola, and it then flows downwards in the hollow space between the walls 40 and 46, and is conveyed, after having passed the other balancing diaphragm 47, to the nozzles and conveyed by them inside the cupola. The structure of the above described cupola allows an adjustable metallurgical working of the cupola itself and in particular:

(1) It allows to obtain, at the sprue basin, cast iron of low carbonium content if the intake pipeline 34 is kept closed by means of the gatevalve 35, while the pipeline 37 is kept open and through it the ventilator 33 sucks fresh air which is conveyed to the nozzles after having been heated in the third hollow space.

(2) It allows to obtain cast iron at high carbonium content if the pipeline 37 is kept closed and the pipeline 34 is kept open, keeping at the same time the valve 10 completely open and consequently restricting completely the passage controlled by the valve 12 for the air sucked from the top of the chimney. In such a way it is possible to obtain a cast iron having the highest carburation, which is higher than that obtainable with normal cupolas, because the gas drawn from inside the chimney through the valve 10 is rich in CO and CO which are conveyed to the nozzles. In this case the mixture of gas and air conveyed to the nozzles has a very high temperature.

(3) The possibility of obtaining cast iron with intermediate carburation between those obtainable according to the (1) and (2) above, by controilling the opening of the valve 10, the valve 12 and closing the gatevalve of the pipeline 37.

Furthermore the cupola according to the invention allows the realization of other important results and advantages among which:

(a) The cupola can work like a normal cupola fed by warm air, if the valve 10 and the pipeline 37 are kept closed, keeping the valve 12 and the gate-valve 35 open for the free passage of the air sucked at the top of the chimney.

(b) The cupola can work like a normal cupola fed by cold air if the pipeline 34 is kept closed by means of the gatevalve 35 and the pipeline 37 is kept open, because the air blown by the ventilator has no time to reach a high temperature while it crosses only the third hollow space.

(0) The conditioning effected by means of the water which runs through the pipe 19 reduces to a minimum and constant value the hydrogen which can be incorporated in the form of little bubbles in the cast iron obtained at the sprue basin, this hydrogen being derived from the decomposition of the water contained in the humidity in the air.

(d) The heating of the air to be sent to the nozzles is obtained without having to burn additional fuel to heat the air itself and this essentially because the heat can be regenerated in the charging zone and along the whole chimney. Such heat would otherwise be lost. In other words an excellent efiiciency is obtained in the cupola. The direct consequence of the heat regeneration effected particularly in correspondence with the chimney and the charging zone is that it is possible to save from 20 to in coke consumption, compared with a cupola of a known type with the same output of smelted cast iron.

(e) A direct consequence of the strong cooling generated by the air which traverses the chimney shell is that the shell itself is made only of metallic sheets without the usual inner protection of fire-bricks with clear advantages during the working and upkeep of the cupola.

(f) Another consequence of the strong cooling generated by the air which is sucked by the ventilator is that the cupola is bounded in the whole charging Zone only by cast iron rings without an inner refractory lining. Such cast iron rings which are more wear resistant than the refractory, greatly reduces the operating expenses as they are easily replaced.

(g) Again because of the cooling generated by the air which is conveyed to the nozzles, the thickness of the lining of the refractory material and of the fire-bricks in the cupola in the preheating zone is much thinner and therefore less expensive than in normal cupolas.

I claim:

1. A cupola furnace comprising a shell defining a sprue basin, a smelting zone and a preheating zone, a chimney on said shell including means for charging the furnace, nozzles in said shell for the supply of gaseous medium to the smelting zone, a wall encircling the chimney to define a space therewith, means controlling communication between said space and the interior of the chimney for admission of exhaust gases to said space, a second wall encircling the shell to define a second space in communication with the first said space, the exhaust gases flowing from the first space to the second space, an inlet for ambient air, a ventilator in communication with the second space and the air inlet for establishing suction therein; valve means controlling the relative amount of gaseous medium supplied to said ventilator from said air inlet and the second space, and means defining a passageway encircling the shell for the passage of gaseous medium from the ventilator to the nozzles in heat exchange relation.

2. A cupola as claimed in claim 1, wherein said shell includes a ring of cast iron elements in the region of said second wall, the cast iron elements and second wall cooperating to define said second space, said cast iron elements having surfaces which are open into the interior of the furnace thereby undergoing heat exchange with the gases therein to in turn heat the gases in said second space and serve as the preheating zone.

3. A cupola as claimed in claim 2, comprising cooling means in the first said space for cooling the gaseous medium therein to produce condensation and thereby humidity control before the gaseous medium is fed to said second space.

4. A cupola as claimed in claim 2, wherein said chimney is constituted solely of metallic sheets.

5. A cupola as claimed in claim 2, wherein said means for charging the furnace is located immediately above the ring of cast iron elements.

6. A cupola as claimed in claim 2, wherein said cast iron elements are superimposed one on another, said elements including transverse flanges extending into said second space with ofiset openings.

7. A cupola as claimed in claim 1, comprising means defining an air-tight enclosure encircling said second space.

8. A cupola as claimed in claim 1, wherein said valve means is a gate valve which is positioned to simultaneously control the amount of exhaust gases and ambient air fed to the ventilator.

References Cited UNITED STATES PATENTS 2,339,192 1/ 1944 Roberson 266-25 2,799,493 7/ 1957 Brownell et a1 26632 2,824,731 2/ 1958 Schwengel 266--32 3,057,615 10/1962 Reece 26630 3,061,296 10/1962 Ulmer 2663O X J. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner. 

